Coating apparatus



Feb. 26, 1963 T. N. CARTER COATING APPARATUS Filed March 25, 1959[JV/[M739 United States Patent Ofiiice 3,078,822 Fatented Feb. 26, 19633,678,822 COATING APPARATUS Thomas N. Carter, Hamilton, Ohio, assignorto Champion Papers Inc, a corporation of Osiris Filed Mar. 25, 1959,$591. No. 891,774 3 Claims. (Ci. 11S33) This invention is concerned withan apparatus for the production of coated substrates, primarily papersubstrates. More particularly, the invention is concerned with anapparatus for producing cast coated substrates wherein an aqueoussuspension including a mineral pigment such as clay or calcium carbonateand an adhesive, such as casein, is applied to the substrate and, priorto drying and while still in a moldable state, the coated surface ispressed against a polished metal surface, such as a rotating drum orendless belt, and subsequently dried to reproduce on the coating surfacea mirror image of the surface against which it is dried. The resultantcoated substrate, primarily coated paper, is characterized in that it isprovided with an exceptionally fine printing surface of high absorbencyand smoothness, enabling the use of printing techniques and theexcellent reproduction of printed material of a quality not fullyrealized with other types of coated papers. This method is described inPatent 1,719,166, dated July 2, 1929, issued to Donald B. Bradner.

By paper, is meant a substrate which is formed on a Fourdrinier orcylinder machine regardless of its basis weight or such distinction asmight be made between paper and, for example, board, as is customary inthe industry.

The present invention therefore has broad application in the paperindustry and represents an improvement over the apparatus and method ofcoating paper as shown, for

example, in Patent 2,316,202 dated April 13, 1943, issued to EdgarWarner.

One of the problems encountered in the manufacture of cast coated papersis that of manufacturing speeds. Another problem is cost of manufacturewhich is a function of not only speed of manufacture but also the costof raw materials. Still a further problem is that of securing a properraw stock upon which the cast coated product may be formed.

Various proposals have been made in attempts to solve one or more ofthese problems. Such proposals have included machine coating of the baseraw stock prior to cast coating, and even more recently, combining a precoating operation with the cast coating operation to obtain theadvantages of a wet precoat, among others, as described in the copendingapplication of Edgar Warner, S.N. 797,123 filed March 4, 1959. All ofthese proposals have merit and as such have some effect on the results,but prior to the development of the present apparatus the advantages tobe gained from the most promising of the proposals, namely thatdisclosed in the aforesaid Warner application, have not met with thesuccess believed to be desirable.

It has been found that the apparatus disclosed herein may be usedtoperform the aforesaid method and that the costs of cast coated papermay be reduced somewhat due to the increased speeds with which thecoating and casting operation may be carried out.

An object of the invention is to produce an apparatus for themanufacture of cast coated paper.

Additionally, an object of the invention is to produce apparatus formanufacturing a cast coated paper of superior quality and at less costthan was heretofore possible.

A further object of'the invention lies in the development of apparatusfor manufacturing coated paper of superior quality and at greatermanufacturing efficiency than heretofore possible.

These and other objects of the invention not specifically set forth butnonetheless inherent therein, may be accomplished by providing acombination of a web tensioning means for flattening the substrate as itis fed into the coating equipment, said means acting to relieve thetension as the substrate is fed into a precoating unit and meansdisposed behind the precoating unit for doctoring or trowelling in theprecoat, followed by means for applying a final coating to the precoatedsubstrate immediately prior to the means for molding the coating anddrying same. Preferably the distance between the doctoring or trowellingmeans and the final coating means is maintained at a minimum, inaccordance with method in aforesaid copending application of EdgarWarner.

Having referred in general terms to the nature and objects of theinvention, a detailed description thereof will now be set forth. Indescribing the invention, reference Will be made to the drawing appendedhereto and forming a part of the specification which comprises a sideelevational view of the novel apparatus which may be used in effectingthe method referred to hcreinabove.

It will be seen from an inspection of the drawing that the substrate Sis mounted in roll form on an unwind stand 1. This stand is adapted toreceive a roll of raw stock 3 which has been wound on a suitable mandrel5. The mandrel 5 has its ends removably fixed in a pair of journals 7(only one shown). Preferably, a braking mechanism 9 is associated withthe journals 7 such that the rate of rotation of the mandrel 5 may bevaried. As shown in the drawing, the brake mechanism is in schematicform since there are available on the market several types of brakingdevices which may be used to produce the desired result.

From the unwind stand 1 the substrate, as a continuous web, S, isthreaded over a pair of guide rolls 11 and 13 which are mounted on aframe 10 by means of a pair of identical depending arms 17. The rolls 11and 13 serve to flex the substrate to condition it, i.e., aid inremoving wrinkles and the entrapped stresses which are formed thereinduring its manufacture, prior to the time the web enters the coatingoperations.

From the rolls 11 and 13 the substrate is passed over a rubber coveredtension regulating roll 19. This roll 19 is mounted in suitable journalson the frame 10 and is characterized in that it is a driven roll, beingdriven by belt 21 through a variable speed transmission 20 which derivesits power from shaft 22 which in turn is driven from the same primemover 25 that drives the mechanism imparting movement to the travelingsurface against which the coated substrate is to be pressed and dried.The surface of the rubber covered roll is such that the frictiongenerated between web and roll surface is sufficient to prevent slippagebetween the substrate and the roll surface.

In carrying out the operation of the apparatus thus far described, therubber covered roll 19 is driven at a speed slightly in excess of thespeed of the substrate S as measured at a point between roll 13 and thelead in side of the roll 19. The effect of this arrangement is tomaintain a tension between rollstand 1 and regulating roll 19 and toreduce and maintain a substantially constant tension in the web betweenroll 19 and the first coating operation. This reduction in tension onthe feed-off side of the roll 19 is possible because of the fact thatthe substrate possesses inherent stretchability, up to .6% per unitlength. Thus the substrate is stretched into the lead in side of roll 19because the friction is SllffiClCIliI between roll 19 and the substrateto cause it to be put under tension and stretched. However, as

the substrate passes to the feed-off side of the roll it contracts to asubstantially zero stretch, i.e., the stretch induced by roll 19 isdissipated, with the net result being that the tension is reduced fromone-half to two-thirds or more of its value on the unwind side of theroll 19, but is constant.

From the tension regulating roll 19 the substrate is threaded beneath afurther guide roll also mounted on the frame 10. Guide roll 15 is notdriven. From guide roll 15 the substrate is passed into the precoatingoperation. The precoater, so called to distinguish it from the finalcoater, is comprised of a driven color roll 24 partly immersed in thecoating suspension provided by suitable feeding means to a trough-likepan 26. This color roll 24 may be rotated in either direction and servesto pick up coating from the pan 26 and carry it onto the substrate S.

From the color roll 24 the substrate is fed into a trowelling anddoctoring apparatus 30. This apparatus consists of a pair of spacedrolls 32 and 34 and a doctor blade 48. The rolls 32 and 34 are mountedfor vertical adjustment in a pair of vertically slotted depending arms36. Each of the adjustment means may comprise a. journal block 38slidable in slot 40 and fixed in the desired position by means of avertically disposed threaded hanger bolt 42 attached to the journalblocks 38 and passing upward through a horizontal ear or lug 44 andlocked thereto by a nut 46.

The rolls 32 and 34 are as indicated, spaced in the direction of travelof the substrate S through the apparatus. Disposed in this interveningspace and fixed to the frame 10 is the doctor blade 48. Preferably, thedoctor blade is a rotating doctor, such as shown in Patent 2,598,733issued June 3, 1952 to Edgar Warner. It will be noted that therelationship between the doctor blade 48 and the rolls 32 and 34, oneeach of which immediately precedes and immediately follows the doctorblade 48, is such that the substrate is caused to break over the doctor48 in a generally serpentine path. This arrangement, coupled with theconstant tension in the web as controlled by roll 19, causes the coatedsubstrate to draw against the doctor blade 48 and results in atrowelling of the coating into the interstices of the paper.

Since there are various factors which affect the degree of trowellingand doctoring action that the doctor blade 48, among the more importantof which are, the angle at which the substrate passes over the doctorblade and the amount of break effected thereover, it may be seen thatbecause the rolls 32 and 34 are vertically adjustable relative to thedoctor, they may be adjusted to vary both the approach angle of thesubstrate S and the degree of break over the doctor blade 48.

The substrate is thus precoated, the precoat consisting of an aqueousdispersion of an adhesive and a mineral pigment having been appliedthereto and thoroughly trowelled onto the surface of the paper. From theprecoating operation the substrate S travels in a horizontal path fromroll 34 to a roll 52 which rotates in the direction of movement of thesubstrate.

From roll 52 the coated substrate is passed into a final coatingapparatus 50 including a color roll 51 where it receives a furthercoating of the aqueous suspension of adhesive and mineral pigment beforeit is pressed into contact with the polished non-adherent surface 100shown in the form of a rotating drum. Preferably, the second coating iscomprised of the same mineral pigment and adhesive, but the slurry maybe less viscous than that applied at the precoater.

The drum 100 or other means is driven from a prime mover which as hasbeen indicated is that which also drives the tension regulating roll 19through the variable speed transmission 20. With the peripheral speedaforementioned Warner Patent 2,316,202 and need not therefore bedescribed in detail. It will be noted that the final unit 50 acts toflood the still wet substrate with an excess of coating prior to thetime it passes into the nip defined between press roll 51 and polishedsurface of drum or other supporting medium 101.

The novel combination of apparatus described is highly effective incarrying out the referred to Warner method of cast coating paper. Anessential operation performed by the apparatus is that proper tensioningof the web throughout the entire operation to assure proper operation ofeach phase of the coating application which results in a continuous castcoating operation at an increased speed over that which has beenrealized before.

Having described the invention, both novel method and novel apparatusfor the production of cast coated papers, it will be apparent thatchanges and modification thereof will occur to one skilled in the artand which are within the spirit and scope of the inventive conceptlimited as it is only as defined hereinafter, where- What is claimed is:

1. An apparatus for manufacturing coated paper comprising a frame; atension control means, a plurality of coating applicator means and arotatable casting drum and press roll defining a nip mounted in sequenceon said frame; an unwind stand associated with said frame, for playingoff a web of paper under tension from a roll carried thereon throughsaid tension control means, said plurality of coating applicator meansand onto said casting drum; drive means mounted on said frame andconnected to both said casting drum and said tension control means; saidlast mentioned means comprising a rubber covered roll in contact withsaid web over at least half its circumferential surface and said drivemeans including a variable speed transmission means whereby therelationship of speed between the nip defined between said press rolland said drum and said rubber covered roll may be varied to produce aconstant tension in said web from said drum, irrespective of variationsin tension which may occur between said unwind stand and said rubbercovered roll.

2. An apparatus as defined in claim 1 wherein the first of said coatingapplicator means comprises a color roll and a doctor means including ablade disposed transversely to the path of movement of the web and incontact therewith and adjustable roll means immediately preceding andfollowing said blade for adjustably controlling the angles at which theweb passes over and leaves the line of contact with said blade.

3. An apparatus as defined in claim 1 including further roll meansmounted on said frame interposed between said unwind stand and saidtension regulator means, said roll means being arranged to cause saidweb to flex first in one direction then in the opposite direction beforeits entry into said tension regulator means.

References Cited in the file of this patent UNITED STATES PATENTS956,602 Pulsifer May 3, 1910 2,631,561 Calton Mar. 17, 1953 2,678,284Holt May 11, 1954 2,678,890 Leighten May 18, 1954 2,810,966 BicknellOct, 29, 1957

1. AN APPARATUS FOR MANUFACTURING COATED PAPER COMPRISING A FRAME; A TENSION CONTROL MEANS, A PLURALITY OF COATING APPLICATOR MEANS AND A ROTATABLE CASTING DRUM AND PRESS ROLL DEFINING A NIP MOUNTED IN SEQUENCE ON SAID FRAME; AN UNWIND STAND ASSOCIATED WITH SAID FRAME, FOR PLAYING OFF A WEB OF PAPER UNDER TENSION FROM A ROLL CARRIED THEREON THROUGH SAID TENSION CONTROL MEANS, SAID PLURALITY OF COATING APPLICATOR MEANS AND ONTO SAID CASTING DRUM; DRIVE MEANS MOUNTED ON SAID FRAME AND CONNECTED TO BOTH SAID CASTING DRUM AND SAID TENSION CONTROL MEANS; SAID LAST MENTIONED MEANS COMPRISING A RUBBER COVERED ROLL IN CONTACT WITH SAID WEB OVER AT LEAST HALF ITS CIRCUMFERENTIAL SURFACE AND SAID DRIVE MEANS INCLUDING A VARIABLE SPEED TRANSMISSION MEANS WHEREBY THE RELATIONSHIP OF SPEED BETWEEN THE NIP DEFINED BETWEEN SAID PRESS ROLL AND SAID DRUM AND SAID RUBBER COVERED ROLL MAY BE VARIED TO PRODUCE A CONSTANT TENSION IN SAID WEB FROM SAID DRUM, IRRESPECTIVE OF VARIATIONS IN TENSION WHICH MAY OCCUR BETWEEN SAID UNWIND STAND AND SAID RUBBER COVERED ROLL. 